Computing systems typically allocate memory using a regime that guarantees the continued availability of the allocated memory. If a memory consumer requests an allocation of memory and there is sufficient free memory to satisfy the request, then the request is granted. The memory consumer may subsequently use the allocated memory until the memory consumer process terminates or explicitly releases the allocated memory. If sufficient free memory is not available to accommodate the memory allocation request, then the request is denied. Certain memory consumers are tolerant of being denied a memory allocation request, but some memory consumers fail catastrophically if they are denied a memory allocation request. Some kernel space memory consumers are intolerant of being denied memory allocation requests as they are critical to the proper operation of their respective systems services. To avoid catastrophic failure of these critical memory consumers, many computing systems are configured to operate with a significant reserve of memory that purposefully remains idle.
For example, in a conventional virtual machine (VM) setting, proper execution of each VM depends on an associated virtual machine monitor (VMM) having sufficient memory. The VMM may request a memory allocation during normal operation. If a host system has insufficient memory for the VMM at some point during VM execution, then the VMM is forced to kill its VM. If the average amount of idle memory falls below a predetermined threshold, then the host system may be reconfigured to reestablish a certain minimum amount of idle memory. Process migration may be used to rebalance VM system loads among host systems, thereby increasing idle memory on the host system encountering memory pressure. While maintaining an idle memory reserve serves to avoid catastrophic failures, this idle memory represents a potentially expensive unused resource.